Grid Unlocked: How Street Networks Evolve as Cities Grow

A new study purports to be one of the first to look at how urban areas develop over time and how their informal layouts become rationalized into a distinct grid. The study possibly discounts the work of Bill Hillier and Julienne Hanson who have worked for more than 30 years on a systematic study of urban morphology and using graph theory developedSpace Syntaxas well as the work ofMIT’s City Form Research Group, but nevertheless is interesting in its corroboration of many of the ideas and postulates of these systems. maybe its not the system but the process of investigating evidence based or grounded theory? From Scientific American by Sarah Fecht

Before urban planning, street patterns emerged organically. Understanding the fundamental and man-made forces behind the growth of streetscapes could help guide the development of today’s cities.

Evolution of the road network from 1833 to 2007. For each map we show in grey all the nodes and links already existing in the previous snapshot of the network, and in colors the new links added in the time window under consideration. (b) Map showing the location of the Groane area in the metropolitan region of Milan. (c) Time evolution of the total number of nodes N in the network and of the total population in the area (obtained from census data).

The world’s cities are absorbing one millionadditional people every week—and by 2030, they could consume an extra 1.5 million square kilometers of land, or roughly the area of France, Germany and Spain combined. What would be the best ways for those cities to grow? A new study examines how—before urban planners existed—a group of Italian villages evolved into suburbs outside Milan today. Such studies may eventually help planners optimize future developments.

“We know few things about how cities grow naturally,” says Emanuele Strano, a doctoral candidate studying urban geography at Switzerland’s École Polytechnique Fédérale de Lausanne who authored the study. “Urban planners believe that with regulations we can control the growth of cities. The question is, how can we control a thing if we don’t really know how it behaves?”

The new study takes a step toward that essential understanding. Strano and his colleagues—a group of computer scientists, mathematicians, physicists and urban scholars—teamed up to provide the first quantitative analysis of how unplanned street networks evolve over time. Their results were published March 1 in Nature‘s “Scientific Reports.” (Scientific American is part of Nature Publishing Group.)